Insulated windows comprise an assembly of multiple substrates (generally glass) in a spaced apart configuration with air or other insulating gas sealed in the void between the substrates. If the seal is broken, moisture can enter the assembly which condenses on the glass and clouds the window and also reduces its insulating properties.
A spacer around the periphery of the substrates maintains the substrates in the spaced apart configuration. Commonly a sealant material is applied around the perimeter of the assembly in the channel between the edges of the substrates and the spacer material to prevent the seal from breaking due to separation of the substrate from the spacer and to prevent penetration of moisture through the spacer. Examples of devices for sealing an assembly perimeter are shown in U.S. Pat. No. 4,826,547 issued to Lenhardt, and in a previous application to the present inventor under U.S. Ser. No. 08/694,666.
Some spacers, particularly those including polybutylene, or other butyl materials, or combinations of multiple sealant materials, particularly including polymeric materials such as polysilicones, EDPM, and polyurethanes, have been found to have excellent sealing properties in contact with the inner surfaces of the substrates without an additional layer of sealant material.
At the corners, however, the insulation, sealing and moisture barrier properties may be reduced. Ends of the spacer are generally joined at the corners. In other cases the spacer is bent or folded to form a corner. It is preferred to cut or notch the spacer partially to form a square folded corner without bulging or wrinkling. At the cut, notch, or join additional sealant is preferably applied to maintain the integrity of the seal. For the greatest efficiently the sealant material must join with the spacer to form an airtight seal with the glass surfaces and the spacer material. Thermoplastic materials such as butyl materials are commonly used. In a preferred assembly the spacer and sealant are selected to be compatible to form a chemical bond between them. Since the entire perimeter of the glass assembly will not be filled with sealant material, the spacer can advantageously be placed close to the edges of the assembly reducing excess glass costs. The shallow channel between the spacer and the edge is used to spread sealant material in a smooth layer from the corner area. Significant savings in both time and material can be achieved if only the corners are to be sealed, particularly using an automated method and apparatus.